1. Field of the Invention
This invention relates to fillers and more specifically it relates to fillers modified with polyvinyl alcohol and cationic melamine-formaldehyde resin.
2. Description of the Prior Art
U.S. Pat. No. 4,258,103 discloses a coating used in the preparation of a decorative heat and pressure consolidated laminate wherein the coating comprises an inert filler, a non-thermoplastic adhesive (for example, polyvinyl alcohol) and a water soluble thermosetting resin selected from the class consisting of urea-formaldehyde resin condensates and melamine-formaldehyde resin condensates. The melamine-formaldehyde resins described in this patent are not cationic.
It is known that polyvinyl alcohol by itself does adsorb onto mineral filler surfaces to some extent ("Polyvinyl Alcohol Properties and Applications," Chapter 13, pp. 331-338, John Wiley & Sons, 1973). Clay, for example, commonly is used in conjunction with polyvinyl alcohol as a binder for coatings for paper substrates. The reference also shows that much of the polyvinyl alcohol charged in such a system often remains unadsorbed and is wasted in the water phase.